feat: Rewrite conversation/labelMixin to a composable (#9936)

# Pull Request Template

## Description

This PR will replace the usage of `conversation/labelMixin` with a
composable

Fixes
https://linear.app/chatwoot/issue/CW-3439/rewrite-conversationlabelmixin-mixin-to-a-composable

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

**Test cases**

1. Add/remove labels from conversation sidebar
2. See labels are showing up dynamically
3. Check add/remove labels working fine with CMD bar
4. Check card labels in conversation card and SLA reports table.


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

app/javascript/dashboard/mixins/conversation/labelMixin.js

@@ -1,46 +0,0 @@
-import { mapGetters } from 'vuex';
-
-export default {
-  computed: {
-    ...mapGetters({ accountLabels: 'labels/getLabels' }),
-    savedLabels() {
-      // If conversationLabels is passed as prop, use it
-      if (this.conversationLabels)
-        return this.conversationLabels.split(',').map(item => item.trim());
-      // Otherwise, get labels from store
-      return this.$store.getters['conversationLabels/getConversationLabels'](
-        this.conversationId
-      );
-    },
-    // TODO - Get rid of this from the mixin
-    activeLabels() {
-      return this.accountLabels.filter(({ title }) =>
-        this.savedLabels.includes(title)
-      );
-    },
-    inactiveLabels() {
-      return this.accountLabels.filter(
-        ({ title }) => !this.savedLabels.includes(title)
-      );
-    },
-  },
-  methods: {
-    addLabelToConversation(value) {
-      const result = this.activeLabels.map(item => item.title);
-      result.push(value.title);
-      this.onUpdateLabels(result);
-    },
-    removeLabelFromConversation(value) {
-      const result = this.activeLabels
-        .map(label => label.title)
-        .filter(label => label !== value);
-      this.onUpdateLabels(result);
-    },
-    async onUpdateLabels(selectedLabels) {
-      this.$store.dispatch('conversationLabels/update', {
-        conversationId: this.conversationId,
-        labels: selectedLabels,
-      });
-    },
-  },
-};